ABCD

Example

A
B
B
7
B
B
C
15
B
A
C
_
7
7
_
 
 
A
B
C
_
_
_

Solution

A
B
B
7
B
B
C
15
B
A
C
13
7
7
21
 
 
A
B
C
1
3
9
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ABCD
ABCD

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